Which process is responsible for pulling air into the lungs?

• A. Internal respiration
• B. Negative pressure during inhalation
• C. Positive pressure generated during exhalation
• D. Diffusion of oxygen

Answer: (B)

The process responsible for pulling air into the lungs is negative pressure during inhalation. This occurs when the diaphragm and intercostal muscles contract, leading to an increase in the volume of the thoracic cavity. As the volume increases, the pressure within the lungs decreases relative to the atmospheric pressure outside the body. This difference in pressure allows air to flow into the lungs from an area of higher pressure (the outside environment) to an area of lower pressure (the thoracic cavity). This mechanism is a fundamental aspect of pulmonary ventilation and is essential for proper gas exchange in the lungs.

Understanding the role of negative pressure is crucial for grasping how respiratory mechanics function during inhalation and exhalation. During the latter phase, the muscles relax, and the elastic recoil of the lungs and chest wall creates a positive pressure that drives air out of the lungs, but it is the negative pressure generated during inhalation that is primarily responsible for drawing air in.